Laser scanning is a mensuration technique which has been used to collect data points from the surface of a three-dimensional article. The data points correspond to coordinate values over the surface of the scanned article, e.g. taken along the X, Y, and Z axes. The laser scan head traverses a scan path over the surface of the article, and at selectable distances along the path point values may be taken. The laser scan generally results in generation of a set of scan data in a digitized format.
The further use of the laser scan data in practical manufacturing application has been limited due to a number of factors. One factor is the great magnitude of data which must be processed relative to other mensuration techniques. Another factor is the limited ability of extant laser scan software algorithms to recognize or differentiate surface transition features (corners, vertices, openings, boundaries, etc.) of the scanned article. Yet another factor is the incompatibility of CAD/CAM software to the laser scan data file format. Still another factor is the difficulty in correlating the scan path of the laser head to a desired tool path for a numerically-controlled machine tool. A correlation between the laser scan path and the NC tool cutting path may result in gouging or scalloping of the work. These limitations become pronounced when laser scanning is used for capturing the geometry of parts such as automotive trim parts. These features are typically complex free-form shapes and require many measurements to accurately define the shapes. Determining the true position of their free form surfaces can be quite difficult.
In the automotive industry, as representative of the manufacturing field, an established mensuration technique is the coordinate measuring machine (CMM). A CMM uses a mechanical probe which traverses a path covering the surface of the article to be measured. CMM machines typically work with algorithms that recognize part features, such as edges, from user supplied nominal locations. A CMM process, however, is slow, interactive and operator intensive. In comparison, laser scanning is not highly interactive but it has required feature determination off-line through statistical processing.